So you think that Novell+SUSE (and without Ximian) would have tried to ban KDE altogether? Because that's what's actually happened a short while after SUSE was bought.
Do you think that Novell+SUSE would have another MS fanboy like De Icaza who's pushing stuff like Mono?
I really don't think so, especially as openSUSE+KDE doesn't even install by default and KDE is still maintained by the old SUSE team.

The Ximian guys took the lead in Novell's Linux division simply because they were the first in that division. If Novell bought another Linux company first, its managers would've taken the lead in the division.

If Novell bought SUSE first, Novell may never even bought Ximian at all. Hey, maybe Novell would've bought Trolltech or a former "United Linux" partner.

if I were selling a Linux distro I would want to make it a nice target for proprietary developers. Having Qt with the GPL/paid licences made this realistically impossible

Neither SLED nor SLES are primary targeted towards developers. Just count the number of proprietary GTK apps on Linux that are actually distributed.

The GPL is not an issue for internal development, because internal deployment is not distribution (check GPL FAQ if you don't believe me).
And even if Novell+SUSE would propagate GTK for development, that has nothing to do with the default DE. openSUSE KDE installs Firefox by default as well.